Conventional gas turbines comprise an inner casing and an outer casing. In particular, the inner casing separates the working fluid of the turbine from the environment. The inner casing separates in particular the inner volume of the gas turbine from the outer volume of the turbine. To the inner casing, the stator vanes of a turbine section or of a compressor section are mounted. The outer casing surrounds the inner casing, wherein generally between the inner casing and the outer casing a cooling air cavity and a cooling air duct, respectively, is formed.
Leakage of cooling air and of working fluid between the inner and outer casing is needed to be prevented in order to avoid that the cooling air, in particular of the turbine section, escapes. At the same time a simple and reliable assembly of the gas turbine casing parts should be provided.
In conventional gas turbines, along an axial direction of the turbine, a compressor section and a turbine section are mounted together at its axial ends. A seal ring is mounted with one side to an axial end of a turbine section either to the inner casing or to the outer casing and with the other side to an axial end of a compressor section.
FIG. 3 illustrates a conventional gas turbine 300 comprising a conventional power turbine 310 and a conventional gas generator 320 which are mounted together at its axial end. The conventional power turbine 310 comprises an annular conventional outer casing 311 and an annular conventional inner casing 312. The conventional outer casing 311 and the conventional inner casing 312 extend generally annular around a rotating axis 101 of the conventional gas turbine 300. The stator vanes 115 are mounted to the conventional inner casing 312. Between two rows of stator vanes 115, a rotor blade 116 may rotate. Between the conventional outer casing 311 and the conventional inner casing 312, a conventional cooling duct 314 is formed, through which cooling air is flowable. At an axial end of the conventional power turbine 310, a conventional seal ring 313 is attached. The conventional seal ring 313 is mounted to a part of a further conventional outer casing 321 (or a further conventional inner casing 322) of the conventional gas generator 320 and the conventional inner casing 312 of the power turbine 310 for generating a sealing between the conventional inner casing 312 and the further conventional outer casing 321. The conventional seal ring 313 is fixed against axially displacement e.g. by fixation to the conventional inner casing 312 and is in slidable contact with the further conventional outer casing 321, such that thermal expansion in axial direction between the conventional power turbine 310 and the conventional gas generator 320 is provided.
EP 1 426 561 A1 discloses structures for attaching or sealing a space between components having different thermal coefficients or rates of thermal expansion. A sealing element is mounted between a first component and a second component that have different rates or amounts of dimensional change upon being exposed to temperatures other than ambient temperatures. The sealing element comprises a first attachment structure associated with the first component that slidably engages a second attachment structure associated with the second component, thereby allowing for an independent floating movement of the second component relative to the first component. The structure can comprise split rings, laminar rings or multiple split rings.
U.S. Pat. No. 4,613,280 discloses a turbine engine which is constructed to passively modulate the flow of cooling air into the shroud. Seal rings are disposed relative to the cooling air inlets in the shroud such that pressure in temperature variations in the engine will cause the cooling air inlets to be either fully opened completely blocked by the seal ring or modulated therebetween in accordance with the cooling needs of the shroud.
U.S. Pat. No. 4,307,993 discloses an air cooled cylinder with piston ring labyrinths. A turbine cylinder is in contact at its outer surface with split rings which are held in space in annular slots in a cylindrically extending ring holder. The rings, while remaining in contact with the outer surface of the cylinder are allowed to expand and contract within their respective slots.
US 2010/0129207 A1 discloses a steam turbine comprising a rotor and a inner casing, wherein between the inner casing and the rotor a flow passage is formed which on the inlet side is axially delimited by a balance piston which is arranged on a rotor. Moreover, a piston seal is provided between the inner casing and the rotor.
DE 27 44 76 discloses a steam turbine comprising a casing to which a vane carrier is mounted.
In conventional turbine designs, the seal ring, in particular the piston ring, is carried by a part of the gas generator and by another part of the power turbine, so that a sealing arrangement is generated not until the gas generator is fixed to the power turbine. This mounting procedure of the gas generator and the power turbine together causes a blind assembly of the seal ring inside both sections, because during the mounting of the sections, the seal ring is only hardly visible. Moreover, a sealing test of the seal ring in the sealing section is difficult after the mounting of the gas turbine to the gas generator.